Process and apparatus for the continuous gasification of solid fuels



Oct. 10, 1939. v w. UNDER 2,175,610 PROESS AND APPARATUS FOR THE CONTINUOUS GASIFICATION OF SOLID FUELS lFiled Jun 3o, 1957 Patented Oct. 10, 1939 UNITED STATES PATENT OFFICE PROCESS AND APPARATUSl FOR THE CON- TINUOUS GASIFICATION OF SOLIDl FUELS Ware Application June 30, lll/'37, Serial No. 151,112 In Germany :July 4, 1936 2 Claims.

The invention relates to the continuous gasification of solid fuels of all kinds, especially coal, coke, brown coal or the like, by means of a preheated mixture consisting of air and steam .for

5 the purpose of producing combustible gases and more particularly to the gasification of fuel in an essentially vertical shaft throughl which the fuel passes from the top downwards and which is provided at the bottom with a grate suitable for the extraction of solid ash.

The gasification of solid fuels by means of a preheated mixture of steam and air is wellknown per se.4 Such preheating is useful in that the quantity of steam that is to be delivered together with air into the gas generator for reaction with the fuel may be efliciently increased. The higher the quantity of steam that may be added, the greater will be the percentage of the more valuable water-gases that will be formed within the fuel bed. Further, by providing for passing much more steam into the bed, the slag will be cooled-down rapidly and granulated and the dangerous formation of big slag lumps will be avoided.

In the gas producers known hitherto, the shaft is provided at the bottom with a revolving grate by means of which the solid ash may be extracted from the shaft. This revolving grate is equipped with means for the removal of ash or slag in solid form from the gas producer shaft. The commonly used revolving grates are built with a cast-iron body, ttedwith openings for the introduction of air-steam mixture into the fuel bed.

The temperature to which the steam-air mixture maybe heated in a gas producer, provided with s uch a grate, depends on the heat resistance of the material used for the construction of the grate. This temperature lies about at 30D-400 C. for the common forms of cast-iron revolving grates. If the temperature of the preheated steam-air mixture is higher, either the grate will be burnt out too quickly or prematurely, or it will be destroyed by stresses of heat expansion. It is impossible to construct the grate from a refractory material, because such material does not (Cl. l18--203) be drawn-off if the gas generator is operated at a definite minimum temperature, and as the operating temperature is decreased by introducing steam into the shaft, the quantity of the steam to be added to the gasifying air is thus limited and even with a comparatively high preheating of the gasifying air. Hence only a relatively small amount of steam can be introduced in to a shaft of a liquid ash generator.

Now, the principal object of my present invention is to provide such improvements, which will make the operation of the gas producer independently of the unfavourable influences explained above, and which will make it possible to gasify the fuel by means of an air-steam mixture which contains more steam than one was able to add hitherto.

According to the present invention, the highly preheated steam-air mixture is introduced into the fuel column at a Zone situated somewhat above the grate in the lower part of the shaft and simultaneously to introduce cold air or a suitable steam-air mixture into the fuel bed from below is not introduced through the iron generator grate. Notwithstanding the comparatively high temperature of the fuel bed within the gasifying zone, the grate, on the other hand, is also kept cool by the cold air, introduced into the shaft through the grate.

The term cold air means within the scope of this invention, the gasifying media. These gasifying media may consist either of air only, or of air with a certain addition of steam, or moderately preheated air and/or steam. If necessary, it is also possinble to increase the oxygen content of the gasifying air, or to introduce pure oxygen from below into the shaft and to avoid an increase of the temperature of the fuel bed in the neighborhood of the grate by an increased amount in the addition of steam to the colder air.

In order that this invention may be more readily understood and carried into practice, reference is hereby made to the accompanying drawing showing in a vertical section the gas producer built according to the invention. The gas gener.. ator consists of the gasiiier I and the liner 2, made of refractory brickwork. The upper part of the gas producer is fitted with a fuel feeding arrangement 3 and an outlet for the useful gas. The gasifier shaft shows a slightly conical tapering in the lower part, which corresponds to the reduced quantity of fuel. The shaft is equipped below with a revolving grate 5, which discharges the ash from the shaft into a trough 6. The revolving grate 5 is for instance, provided with an upper central hood 1, fitted with openings, said hood being connected with a pipe 8 for the supply of the air-blast. The air main I0 controlled by a valve 9 is connected to the steam line I I and to the pipe 8, regulated by a valve I2. Above the grate hood 'l of the revolving grate there is arranged in the gasier wall quite a number of nozzle openings I3, I4 and I5. These openings are formed by means of water-cooled nozzles I6, which are situated in a protection frame I1, so that they can be exchanged. Refractory lined pipeline branches I8, I9, 20 are connected with the nozzles I6. The pipeline branches I8, I8 and 20 are coupled with a distributing pipe 2| and, if necessary, suitable regulating members may be inserted.

The distributing pipe 2| is supplied with the steam-air mixture which has been brought to a high temperature in a suitable gas heater, which may, for example, comprise a set of regenerators, which are heated-up alternately, with a part of the generated useful gas.

The temperature of the steam-air mixture may be increased in the gas heater therefor, so that a considerable quantity of steam may be led into the gasifying shaft, together with the gasifying air, in order to be used there for reaction with the fuel. This is of special importance for gasifying bituminous fuels, for example brown coal. During the gasification process of such fuels, a considerable quantity of waste liquors is produced in the cooling and purifying process for the useful gases. The waste liquor is contaminated with organic acid constituents, such as phenol or other tarry matters.' The quantity of the so-called low-temperature liquor is so high, that it could not be dealt with in the gas producers as heretofore known and operated. On the other hand, a different special treatment of the low-temperature liquor is often troublesome. This low-temperature liquor on account of its poisonous constituents, is not allowed to be discarded into the natural water draina'ges, without a suitable pretreatment. The invention now offers the possibility to destroy, by a very high heating of the steamair mixture, producer, at the same time making a producer gas of a higher caloric value, since by the now permissible preliminary very high heating of the steam-air` mixture, the fuel bed can react with an amount of steam great enough to take up all such waste liquor if such waste liquor is employed as the source of aqueous medium for the steam for the highly heated air-steam mixture.

I have now described my present invention on the lines of a preferred embodiment thereof, but my invention is not limited in all its aspects to the mode of carrying it out as described and shown, since the invention may be variously embodied within the scope of the following claims.

I claim:

1. A method of continuous gasification of solid fuels by reaction thereof with a mixture of preheated air and steam comprising; maintaining a bed of continuously descending fuel; charging the fuel at the top of the bed and withdrawing the made gas continuously from the upper part of the bed; subjecting the fuel in the lower part of the bed to continuous mechanical rotative agitation and ash crushing action and continuously discharging the ash thereof in solid form from the bottom of the bed; introducing a mixture of very highly preheated air and steam into the fuel bed through the circumference thereof at a zone somewhat above the region of mechanical agitation and flowing the same upwardly through the bed for reaction therewith and withdrawal at the upper part thereof; and concurrently with the introduction of the very highly preheated air and steam separately introducing steam and relatively cooler air into the lower portion of the bed through the mechanical agitation medium to cool the same and diffusing the steam and relatively cooler air from the mechanical medium into the portion of the fuel bed between said mechanical medium and the region of entrance of the very highly preheated air and steam for combustion of combustible residues of the ash and flowing the gas thereof upwardly through the fuel bed for off-flow therefrom together with the very highly preheated air and steam introduced to the fuel bed circumferentially thereof somewhat above the mechanical medium.

2. A gas generator comprising a shell having a fuel bed gasification chamber, an upper fuel 4charging inlet and an upper gas outlet for said chamber; mechanical grate means in the base of the chamber for diffusing gas into the fuel bed therein and rotatively crushing the ash thereof and continuously discharging the same from the fuel bed continuously at the base thereof; means for supplying a mixture of very highly preheated air and steam to the fuel bed chamber, said means being connected with the circumference of the chamber through circumferential inlets somewhat above the level of the top of the mechanical grate means; and separate means for supplying relatively cold air to the fuel bed concurrently with the operation of the means for supplying very highly heated air and steam, said mechanical grate means comprising elements for conveying and diffusing gas into the base of the fuel bed, and said means for supplying relatively cold air communicating with said elements of the mechanical grate means to convey the relatively colder air thereto for cooling the grate means by the relatively cold air and discharge of the colder air into the fuel bed for simultaneous flow upwardly through the same to the upper gas outlet together with the flow of very highly preheated air and steam from the circumferential inlets, and steam supply means connected with the grate means for flow of steam along with the relatively cold air through the elements of the grate means.

WILLY LINDER. 

